Major emphasis is placed upon the study of tumor antigens of the transplantation rejection type (TSTA), and of tumor antigens (TA) assayed by in vitro techniques and of the immune responses they evoke. As a corollary to this study the biologic properties in vitro and in vivo of alien histocompatibility (H-2) antigens in several neoplasms are under study. Solubilization and methods of purification of TSTAs are under investigation with the ulimate purpose of defining these membrane and cytosol antigens after purification in physicochemical, biologic and molecular terms.